Author Topic: Test run on Cloudcar Prop, new heads, exhaust and intake  (Read 2505 times)

Schmleff

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I wish all the guys talking about propellors would stop talking about "cavitation".  Cavitation only happens in a liquid.  Webster's definition is "the rapid formation and collapse of vapor pockets in a flowing LIQUID in regions of very low pressure."  Unless your prop is on a boat, and under water, it can't cavitate.  It can operate in a stalled condition, which high pitch props will due at very low forward speeds, but it can't cavitate.  OK?
:-*

I have three videos of three different low passes. Each one has a different prop and each sounds different. I will spice them together and post them. You can hear the 60" "beating the air".
« Last Edit: Jun 05, 2011 by Schmleff »
Jeff Lange
Sonerai I
N1463J

Buy the best and cry once - Gene Berg

Schmleff

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Ok, here is the video.

First the Prince 48x50 (tip speed 915fps)

Second the Cloudcars 52x60 (tip speed 998fps, likely transsonic)

Third the Cloudcars 52.5x56 (tip speed 824fps)

All of these passes are around the mid 190's. Its hard to tell the difference between the exhaust noise and prop noise at first. Listen to how much louder the second prop is.

The Prince and the 52x60 are louder. The last prop is much quieter and the exhaust noise is very distinct. I am not offering definitive answers as to why, but here is a difference between the three.

[yt=425,350]http://www.youtube.com/watch?v=ckzObR8BwqM[/yt]


« Last Edit: Jun 05, 2011 by Schmleff »
Jeff Lange
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Buy the best and cry once - Gene Berg

thomefran

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You can hear the difference.  Why is last one quieter.
Thom Francis
Sonerai II LT
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Regret is valid only when you are too old to correct it.

Schmleff

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I "think" because the Prince has to much area at the tip. The 52x60 does not have enough blade area for my drag profile and its over speeding the tips.

I am not sure. I am in data gathering mode.
Jeff Lange
Sonerai I
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Buy the best and cry once - Gene Berg

n3480h

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Oh baby!  Number three gets my vote, lol.  Sounds extremely powerful.  How can I send this clip to my son?  He should hear what a good VW sounds like.

Tom

PS. found the link.
« Last Edit: Jun 06, 2011 by n3480h »
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Schmleff

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Its on Youtube, just click on their logo and copy the link.

So far, #3 is the best prop for the plane. I have one more test prop coming and then Jay is going to cut me another one based on what we learn.  ;D
Jeff Lange
Sonerai I
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Buy the best and cry once - Gene Berg

N127PZ

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Wow....very cool sounds like P-51 on the attack !
Prayer does not use up artificial energy, doesn't burn up any fossil fuel, doesn't pollute. Neither does song, neither does love, neither does the dance.
Margaret Mead

 

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